Potassium or something more?

Tedmarx38

Active Member
Friends, I flushed these a week ago and added back nutes the next day. The slurry test yesterday for nitrogen and phosphorous show slightly deficient but potash/potassium (k) was severely deficient.

I’m using the FoxFarms bundle of Big Bloom, Grow Big and Tiger Bloom liquids plus their three low dose powder boosters as per their week x week schedule. Yesterday I did, however, double the Beastie Bloom booster (high in k) by using 1/2 tsp instead of 1/4.

Specifics below but I’ve had this problem before during flowering and as noted my spring water is very close to RO although very alkaline.

My questions: does this look solely like a K deficiency or is something else wrong? And, if it is just K, since it keeps happening should I continue to exceed recommended dosing of that element? (Only the rightmost of these four shows considerable damage but the others show early signs of it too.)

Thanks as always

Details:

Four sativa-dominant photoperiods from seed.
Week 6 of flowering.
2x4 tent is 75 degrees 35% rh
12/12 light schedule
Spyder sf 2000 led 200 watt
Lumens - 50,000
Fox farms ocean forest soil
Alkaline spring water with high ph and low tds.
Watering/feeding at ph 6.3 and using one tsp calmag and 1/4 tsp epsom with feedings along with FF’s recommended nutes by week
 

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Billy the Mountain

Well-Known Member
How are you measuring levels of N, P, and K levels from a slurry test?
As far as I'm aware, that's not possible without sending it off to lab for analysis ($$$)
Or maybe you have a mass spectrometer at home?
 

cannabiscrusader

Well-Known Member
Your rh is a touch low causing the plant to transpire at a faster rate. This will give you the slight tip burn you are seeing. Flush was a good call to rid the excess salts left behind by the faster transpiration rate. Those extra salts locked out n and some other macros. Get your rh up just a little bit to 40 or 45 and your issues should be resolved.
 

Tedmarx38

Active Member
Thanks for the helpful insight. The only test I can afford is indeed the luster leaf rapid soil test. I’ve wondered whether it’s suitable because it’s awkward to conduct and does seem to always show low levels.
 
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